One of our proxies is running on OpenBSD 4.2 and when trying to monitor some hosts by DNS names, the following error is written into the log file:
14378:20110113:172100.105 Item [host1:net.if.out[{$NET_IF_ETH},bytes]] error: Get value from agent failed: gethost() failed for address 'host1.network.lan' [Undefined error: 0]
Non-Zabbix utilities like ping and nslookup resolve domain names properly.